joint work with F. Carreiro, Y. Venema and F. Zanasi

Speaker(s)

Alessandro Facchini

Affiliation

Uniwersytet Warszawski

Date

Feb. 19, 2014, 2:15 p.m.

Room

room 5870

Title in Polish

Weak MSO: Automata and Expressiveness Modulo Bisimilarity

Seminar

Seminar Automata Theory

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We prove that the bisimulation-invariant fragment of weak monadic second-order logic (WMSO) is equivalent to the fragment of the modal μ-calculus where the application of the least fixpoint operator μp.φ is restricted to formulas φ that are continuous in p. Our proof is automata-theoretic in nature; in particular, we introduce a class of automata characterizing the expressive power of WMSO over tree models of arbitrary branching degree. The transition map of these automata is defined in terms of a logic FOE∞1 that is the extension of first-order logic with a generalized quantifier ∃∞, where ∃∞x.φ means that there are infinitely many objects satisfying φ.

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